The present invention relates to a method and apparatus for managing communication resources between nodes of a network, and more particularly to a dynamic distributed multi-channel Time Division Multiple Access (TDMA) slot assignment method utilizing speculation slots.
Mobile multi-hop broadcast packet radio networks are known for their rapid and convenient deployment, self organization, mobility, and survivability. In this type of network as illustrated in FIG. 1, a transmission from one node, for example node 1, is broadcast to all nodes in its xe2x80x9cneighborhoodxe2x80x9d. Ultra-high frequency (UHF) systems generally have a neighborhood defined by nodes within line of sight of the transmitting node (these nodes being termed within one xe2x80x9chopxe2x80x9d of the transmitting node). For example, in FIG. 1 nodes 1, 3, 4, 5, 6, 7, and 8 make up one neighborhood. For data transmitted from node 1 to propagate multiple hops, the data must be relayed by one or more of node 1""s neighbors. For example, node xe2x80x9caxe2x80x9d (likewise nodes b, c, and g) is two hops away from the node 1 transmitter. The data will be relayed in this manner until it has arrived at all intended destination nodes.
Since there are generally limitations on the number of simultaneous transmissions that a receiver can successfully process (typically one), collisions can be avoided by the assignment of time slots in which individual nodes can transmit. There are many approaches to deciding which nodes are assigned which slots, and the approach is generally driven by the network applications, such as, broadcast, multicast, unicast, datagrams, virtual circuits, etc. Because the problem of optimally assigning slots in this environment is mathematically intractable, a heuristic approach is taken to design an integrated protocol that both chooses the number of slots to assign to each neighboring node and coordinates their activation in the network.
Tactical military and commercial applications require self-organizing, wireless networks that can operate in dynamic environments and provide peer-to-peer, multi-hop, multi-media communications. Key to this technology is the ability of neighboring nodes to transmit without interference. Neighboring nodes transmit without interference by choosing time slots and channels that do not cause collisions at the intended unicast or multicast receivers. This functionality is provided by the Unifying Slot Assignment Protocol (USAP) which is the subject of U.S. Pat. No. 5,719,868 the disclosure of which is herein incorporated by reference. The function of USAP is to monitor the RF environment and allocate the channel resources on demand and automatically detect and resolve contention resulting from changes in connectivity.
Wireless channel access schemes traditionally come in two flavors: contention and reservation. Contention has been the favorite for ad hoc broadcast networks because its lack of structure lends itself well to the mobile environment. Also, low access delays make it suitable for both tactical voice, where push-to-talk is the norm, and bursty data. However, when the network is heavily loaded contention is inefficient. At that point a structured access like reservation Time Division Multiple Access (TDMA) can achieve much higher efficiencies.
Another division in this field is the difference between broadcast and unicast. Broadcast techniques, in which a node transmits to all of its neighbors, and unicast techniques, in which a node transmits to only one of its neighbors, both have their own unique advantages dependent upon the application. Traditional wireless systems, however, are not capable of utilizing both broadcast and unicast schemes.
Ideally, a wireless channel access system would support both reserved circuits and datagrams in whatever combination is required. Conventional wireless channel access systems however are not capable of supporting both reserved circuits and datagrams.
Conventional wireless communication systems are capable of handling only one or a small number of data types, including low latency voice, delay tolerant data, bursty transactions, high throughput streams, error sensitive data, and error tolerant video. However, conventional systems are not capable of handling the full range of data types.
Conventional wireless communications systems are typically capable of establishing and maintaining only one type of virtual circuit, including either the establishment and maintenance of hard circuits or the establishment and maintenance of permanent datagram service.
Thus, there is a need and desire for a channel access scheme to use TDMA for wireless communication capable of using both broadcast and unicast techniques dependent upon the state of the communication environments. Further still, there is a need and desire for a wireless communication system that is able to handle a full range of data types including low latency voice, delay tolerant data, bursty transactions, high throughput streams, error sensitive data, and error tolerant video. Further still, there is a need and desire for a channel access system that is capable of providing both reserve circuits and datagram service. Further still, there is a need and desire for a wireless communication system that is able to handle the full range of data types while optimizing for densities ranging from fully connected to sparse and, because of its reliance only on local information, scaling to large network sizes.
The present invention relates to a method for automatically managing the communication channel resources between nodes having neighboring nodes in a network of nodes. Each node communicates during specific time slots on a time multiplex basis. The method includes communicating between nodes using a time division multiple access (TDMA) structure having time divisions with time frames, each time frame having time slots during which the nodes may communicate. The method further includes storing, at each node, an assignment of possible time slots to communicate on the network. The method also includes announcing, at a first node to neighboring nodes of the first node, during a first time slot in a particular time frame, an available time slot from the assignment of possible time slots in the particular time frame. The available time slot is arranged subsequent to the first time slot in the particular time frame.
The present invention further relates to a communication system having a plurality of transceiver nodes arranged in a network, each node having neighboring nodes. The nodes are configured to communicate on the network using a TDMA structure which includes time divisions, each time division having time frames, each time frame having time slots. An assignment of possible time slots is stored at each transceiver node and includes possible time slots during which nodes may communicate on the network. A communication access protocol allows a particular transceiver node communication access to an available possible time slot assigned to one of the neighboring nodes of the particular transceiver node.
The present invention still further relates to a method for automatically managing the communication channel resources between nodes having neighboring nodes in a network of nodes. Each node communicates during specific time slots on a time multiplex basis. The method includes communicating between nodes using a TDMA structure including time divisions, each time division having time frames, and each time frame having time slots to communicate between nodes. The time slots include bootstrap slots and standby slots. The method further includes storing, at each node, an assignment of possible time slots to communicate between nodes and identifying an unused standby slot in an upcoming frame based on the assignment of possible time slots.